Economy: Many successful startups have succeeded in a down economy (Microsoft and Google were started in recessions). The truth is a down economy is good for a startup because it weakens larger competitors who need large amounts of money to support their existing infrastructure.
Uncertainty: Job security is a myth. Even if you work for a big company that's secure against going out of business there's nothing to say you won't lose your job tomorrow because of some cost cutting initiative. So you really shouldn't let this become a factor.
Indecision: If you aren't passionate about what type of business you want to start you shouldn't start it. So if this is a problem you should just stay in your existing job.
Debt: If you have good credit you can get a small business loan to ensure you have a consistent salary until you can get customers or VC money. If you have bad credit AND debt you probably shouldn't be starting a business
Family: This is legit. If you have a lot of family obligations you shouldn't start a business
No Benefits: Private benefits actually aren't that expensive. I just checked ehealthinsurance.com and they quoted $79 a month for me. As for 401(k) and such you're making a bet on your new business that it will pay out big for you so you shouldn't really be worrying about retirement for that 2 year period where you're trying to start-up